The principal goals of the proposed research are to determine the pharmacokinetic parameters of adriamycin disposition in children with cancer and the relationship of drug disposition to tumor response. Specific questions that will be asked include: 1. Are there significant interpatient and intrapatient differences in the disposition of adriamycin in children? 2. Does the rate of drug metabolism and the extent of drug distribution significantly influence tumor response in children with neuroblastoma? 3. Does patient age, sex, disease status and/or nutritional status have a predictable influence on adriamycin disposition in children with cancer? The pharmacokinetics of adriamycin and metabolites will be determined from plasma and urine concentrations characterized by a multicompartment pharmacokinetic model using a non-linear least squares regression computer program. Distribution characteristics will be further evaluated from serial bone marrow samples obtained before and after adriamycin administration. Tumor response will be measured by changes in the cell kinetics (Labeling Index, Mitotic Index) of tumor cells obtained from serial bone marrow samples before and after adriamycin administration in children with disseminated neuroblastoma. Previous studies have established the correlation of cell kinetic changes and clinical response in neuroblastoma. Patient variables such as age, sex, concurrent drug therapy, disease status and nutritional status will also be evaluated for their influence on adriamycin disposition. The above study will provide information on the influence of adriamycin metabolism and/or distribution on tumor response in children with neuroblastoma. It may also provide us with a more rational basis for dosage escalation of chemotherapeutic changes in children that fail to respond to current therapy.